Colour photography

ABSTRACT

A process for producing a photographic colour image by the silver dye-bleach process, comprising exposing image wise and processing to a colour image in the presence of a colour bleaching catalyst a photographic material having on a support at least one diffusion-resistant, bleachable image dye-containing silver halide emulsion layer and immediately beneath it on the side away from the light source an image dye-free silver halide emulsion layer. By the present process colour images are obtained wherein the gradation and sensitivity have been favourably influenced.

limited States ateni [191 etilcer et a1.

[ Aug. 28, 1973 1 COLOUR PHOTOGRAPHY {75] Inventors: Alfred Oetlker, Fribourg; Max

Marthaler, Marly-le-Petit, both of Switzerland [73] Assignee: Ciba-Geigy AG, Basel, Switzerland [22] Filed: July 7, 1971 [21] Appl. No.: 160,558

[30] Foreign Application Priority Data July 7, 1970 Switzerland 10265/70 [52] U.S. Cl 96/53, 96/20, 96/73, 96/99 [51] Int. Cl G036 7/00 [58] Field of Search 96/53, 73, 20, 99, 96/3 [56] References Cited UNITED STATES PATENTS 2,697,037 12/1954 .lelley et a1 96/73 2,137,336 11/1938 Gaspar 96/20 3,278,303 10/1966 Meyer et a1 A. 96/53 3,394,004 7/1968 Anderau et a1. 4 96/53 3,650,739 4/1972 Marthaler et a1 96/73 3,708,300 1/1973 Luckey 961/53 Primary Examiner-Norman G. Torchin Assistant Examiner--R. L. Schilling Attorney-Harry Goldsmith et a1.

[57] ABSTRACT A process for producing a photographic colour image by the silver dye-bleach process, comprising exposing image wise and processing to a colour image in the presence of a colour bleaching catalyst a photographic material having on a support at least one diffusionresistant, bleachable image dye-containing silver halide emulsion layer and immediately beneath it on the side away from the light source an image dye-free silver halide emulsion layer.

By the present process colour images are obtained wherein the gradation and sensitivity have been favourably influenced.

15 Claims, 7 Drawing Figures COLOUR PHOTOGRAPHY This invention relates to a process for the production of a photographic colour image by the silver dye bleach process.

A conventional material for the silver dye-bleach process contains at least one emulsion layer dyed with an immage-wise bleachable dye. Such a material is exposed, developed ar 1 finally processed to I a colour image by bleaching the dye as a function of the developed metallic silver and removing the excess silver halide and metallic silver from the material. Particularly important are multi-layered materials for colour images in natural colours which, on a transparent or reflecting support, carry a red-sensitive emulsion layer dyed with cyan dye, above this a green-sensitive emulsion layer dyed with a magenta dye and on top a blue-sensitive emulsion layer dyed with yellow dye. Between these emulsion layers can also be placed filter layers and other intermediate layers.

The known materials and the processes performed therewith have various disadvantages which could not hitherto be completely eliminated. The dyes incorporated in the emulsion layer have in particular a disadvantageous action on the sensitivity of the photographic emulsion. Independent of the spectral range, the sensitivity loss is caused by poisoning of the emulsion with the dyes (chemical desensitising) and, in addition, in those cases where the dyes absorb light, by subduing the light in the layer in the spectral sensitivity range of the light, so that the light exerts no further action deep down in the layer (optical desensitising). Unfavourable colour gradations also often occur which can be corrected only to a limited degree by varying the silver gradation.

Other disadvantages result from difficultly controllable adjacent layer effects. Thus, it was difficult when sufficiently diffusion-resistant dyes were not available to prevent coour adulterations due to colour diffusion. U.S. Pat. No. 2,391,198 proposes a material which has an emulsion-containing separating layer between the emulsion layers dyed with non-diffusion-resistant dyes. According to this patent the image wise developed silver in the intermediate layer serves to bleach any dye which diffuses from the adjacent colour layers. Without the intermediate layer the dye which diffuses into the adjacent colour layer leads to colour changes.

Colour changes also occur when the sensitivity range of the emulsion and the absorption range of the dye are in the same spectral range but do not completely coincide, so that the optical desensitising caused by the dye is dependent on the exposure wavelength. Many attempts have been made to raise the sensitivity of silver dye bleach material, favourably influencing the colour gradation and correcting colour adulterations.

Thus, for example, many of these disadvantages can be avoided by image wise exposing a photographic material having on a support a diffusionresistant, bleachable image dye-containing silver halide emulsion layer and directly thereover on the side facing the light source a silver halide emulsion layer free from image dye having a sensitivity equally as high as the dyecontaining layer and processing to a colour image in i the presence of a colour bleaching catalyst, whereby the colour image is produced exclusively by the image dyes present in the photographic material prior to exposure.

In this process the dye is bleached both under the influence of the silver image produced in the dyed layer and under the additional influence (remote bleaching) of the silver image produced in the overlying colourless layer.

As the additional overlying emulsion layer is free from dye it does not undergo chemical desensitising by the dye. As it is located on the side facing the light source it also does not undergo optical desensitising by the dye. Consequently a higher sensitivity is obtainable in the additional emulsion layer. By according the sensitivities between the dyed and colourless emulsion layers the colour gradation can be influenced, in particular the colour gradation curve can be linearised by correcting the shoulder of the curve.

It has been found that the colour image can also be favourably influenced by bleaching the dye both under the influence of the silver image produced in the dyed layer and under the additional influence (remote bleaching) of a silver image in an underlying colourless layer.

The object of the invention is therefore a process for producing a photographic colour image according to the silver dye bleach process, characterised in that a photographically exposed material which, on a support, has a silver halide emulsion layer containing a diffusion-resistant, bleachable image dye and directly thereunder on the side away from the light source a silver halide emulsion layer free from image dye is image-wise exposed and is processed in the presence of a colour bleaching catalyst to a colour image whereby the colour image is produced exclusively by image dyes present in the photographic material prior to exposure.

The emulsion of the dyed layer and the emulsion of the colourless layer located immediately thereunder can be sensitive in different or preferably identical spectral ranges. These sensitivities may be within or outside the absorption range of the dye and the sensitivities can be at the same or different levels.

Preferably the two adjacent layers are optically sensi' tised with the same sensitiser. It is also preferable for the same basic emulsion to be used for the dyecontaining and the dye-free layers. Insofar as the dye free layer is sensitised in the absorption range of the dye of the overlying layer, it is preferable to work with a material-of low colour density.

Depending on the particular conditions chosen, different effects can be brought out to a varying degree, as will be seen from the following description.

For better understanding reference is made to the schematic gradation curves of FIGS. 1 to 4. These relate to the embodiment wherein the sensitivities of the dyed and underlying colourless emulsion-layer are outside the dye absorption range, so that optical desensitising is not possible. This embodiment, for example, applies to the case where a material is used, which over a colourless green-sensitised emulsion layer has a green-sensitised emulsion layer dyed with yellow dye. On exposing with green light after developing in the upper layer silver image A is obtained and in the lower layer silver image B and after processing colour image C. For comparison purposes, according to the prior art (i.e. without underlying colourless emulsion layer) only silver image A is obtained and therefrom colour image In FIGS. 1 to 4 the colour gradation curve C obtained according to the invention is compared with the colour gradation obtained according to the prior art. It can be seen from the figures that various effects can be obtained as a function of the sensitivity ratio of the two emulsions:

1. if the sensitivity of the lower layer is equal to that of the upper layer, then an effective sensitivity rise and a slight increase in the contrast are obtained.

2. If the sensitivity of the lower layer is of the same magnitude but higher, then there is an even greater sensitivity rise. The arrangements under (1) and (2) are preferred.

3. If the sensitivity of the lower layer is of the same magnitude but lower, then there is a correction of the colour gradation in the bottom portion.

4. If the sensitivity of the lower layer is much greater (i.e. if the lower layer reaches its maximum silver density with an exposure below the threshold sensitivity of the upper layer), then an inflected colour gradation curve is obtained which can be interesting for special effects such as tone separation. Between these extreme cases transitions are possible.

Hence, with increasing silver sensitivity of the underlying colourless layer there is initially a slightly increased contrast (FIGS. 3, 1) then increased effective sensitivity (FIGS. 1, 2, 3).

Analogous effects are observed if the coloured layer and the underlying colourless layer are in different spectral ranges. This embodiment, for example, applies when starting with a material having above a colourless red-sensitised emulsion layer, a blue-sensitive emulsion layer dyed with yellow dye, which is exposed with white light, developed and bleached. Such a layer combination is interesting for obtaining certain masking effects and can also be used as part of a multi-layer, multicoloured material.

Finally, the invention also covers a process with a material whose underlying intermediate layer is sensitive in the absorption range of the dye. Here the same rules apply. This embodiment, for example, applies when starting with a material having above a colourless, red-sensitised emulsion layer, a red-sensitised emulsion layer dyed with cyan dye which is exposed with red light, developed and bleached. Here, in the lower layer, an emulsion with a sufficiently high sensitivity must be used so that this emulsion is effective despite the optical desensitising. Despite the optical desensitising, this embodiment can be successfully employed. This is particularly the case with prints whose colour density in the absorption maximum is only about D I, measured in transparency. However, also with transparencies whose colour density in the absorption maximum is D 2, it is still possible despite the optical desensitising for the underlying emulsionlayer to become effective. It is therefore possible to start with a transparent material which above a colourless emulsion layer sensitised for 660 nm has an emulsion layer dyed with cyan dye with an absorption maximum of 620 nm and sensitised for 620 nm.

As can be seen from what has already been stated, the emulsion of the underlying colourless layer, if sensitised in the absorption range of the overlying dye, must be highly sensitive so that it is effective despite the optical desensitising. Thus, in this case, an emulsion type is used for the underlying emulsion layer which is possibly different from the dyed emulsion layer. It has been found that coarse-grained emulsions can be used without disadvantage for the underlying emulsion layer and that the coarse silver structure of the silver image developed in the additional layer is not noticeable in the colour image.

In other cases the same basic emulsion can be used for the dyed layer and the additional layer. The introduced silver quantity in the colourless layer can thereby be higher, equally high or lower per unit area than that in the colour layer.

With materials according to the invention, it can be seen from thin sections that the silver images of both layers are separated by an area in which practically no silver was developed. This is particularly the case with high colour densities. This is the possible explanation of the new effects obtainable according to the invention. The most favourable relationships between the two layers must be determined empirically from case to case.

Where in this description reference is made to colourless or dye-free emulsion layers this is to be understood to mean that this emulsion layer is free from diffusion-resistant image dye. However, this term does not exclude the possibility of it containing a filter dye, as a result of the presence of which during the exposure the spectral translucency is selectively reduced and/or the image sharpness increased. Such a filter dye is completely destroyed or washed out during processing in baths.

The process according to the invention is suitable for mono-coloured and multi-coloured material. However, it is particularly significant in the production of multicoloured images because the necessity of adapting the gradation and sensitivity of the individual colour layers to one another reduces the number of variation possibilities.

A further advantage of the process according to the invention is that as a result of the dye-free silver halide emulsion layer located directly on the support the disadvantageous action of any roughness can be eliminated, without a special layer being necessary for this purpose.

A multi-coloured material contains at least two silver halide emulsion layers containing image dye, in said layers the image dyes differ from one another and can contain one or more double layers according to the invention. These double layers are separated from other emulsion layers by intermediate layers, and the latter can contain conventional additives such as filter dyes, UV absorbers or oxidising agents. The image dyes are preferably bleachably azo-dyes which must be diffusion-resistant. All layers, both the image dyecontaining layers and the intermediate layers and optionally the bottom and covering layers can'contain the conventional additives such as wetting agents, hardening agents, fog-inhibitors, development accelerators, chemical sensitisers, softeners, and synthetic polymers as gelatine substitutes.

Suitable pyrazines, quinoxalines or phenazines are preferably used as dye bleaching catalysts. These catalysts can be present either in a'photographic processing bath or in a random layer of the photographic material to be processed. The process is suitable for the production of colour transparencies and particularly for the production of colour prints in which, for the support material, there is used, preferably, transparent or pigmented synthetic organic material.

The following Examples will serve to illustrate the invention:

EXAMPLE 1 On a transparent support is cast a 2.5g. thick silver bromide emulsion layer containing 0.3 g. of Ag/m and sensitised for red light. Over this layer is cast a 2.511. thick silver bromide emulsion layer containing 1.2 g. of Ag/m not optically sensitised and containing a yellow image dye. The dye is of formula and is used in a transmission density of 2.3 (material called hereinafter B).

For comparison another material is cast on the transparent support having only the dyed emulsion layer (as above) but no underlying colourless emulsion layer (material A).

Both materials are exposed with white light behind a step wedge and processed according to the following PI'OCCSSI 6 minutes developer pMethylaminophen0l sulphate 2 g. Anhydrous sodium sulphite 50 g. Hydroquinone 6 g. Anhydrous sodium carbonate 20 g. Potassium bromide 2 g. Water to 1000 ml. 2 minutes fixing stop bath Crystallised sodium thiosulphate 200 g. Anhydrous sodium sulphite g. Sodium acetate (3H,,O) 25 g. Glacial acetic acid 13 g. Water to 1000 ml. 4 minutes rinsing minutes colour bleaching bath Water 500 ml. (96%) sulphuric acid 14 ml. Crystallised sodium hypophosphite 1 g. Potassium iodide 20 g. o-Benzoylamino-2,3-dimethyl-quinoxaline 30 mg. Water to 1000 ml. 2 minutes rinsing 6 minutes silver bleaching bath Water 500 ml. (96%) sulphuric acid 27 ml. Crystallised copper-sulphate 20 g. Potassium bromide 60 g. Water to 1000 ml.

2 minutes rinsing 4 minutes fixing bath Composition as for stop fixing bath. 8 minutes rinsing Two colour wedges A and B corresponding to the original are obtained which are measured behind blue filters.

Gradation curves A and B are shown in the graph of FIG. 5. On the abscissa are entered the wedge densities of the exposure wedge (exposure increases from left to right) and on the ordinate the colour density the same applies regarding FIGS. 1 to 4.

It is obvious that with the process according to the invention (B) compared with the process of the prior art (A), a considerable increase in sensitivity is obtained and that particularly in the bottom part the colour gradation is changed.

EXAMPLE 2 A silver bromide iodide emulsion with a 4 mol percent iodide content, 53 g. of Ag/kg and g. of gelatine/kg is prepared. On to a transparent support is cast a layer of this emulsion containing 16 mg/kg of the sensitiser of formula with a sensitising maximum at 640 nm. An identical layer is cast thereover containing mg/kg of the same sensitiser and 15 g/kg of the image dye of formula HOaS NH; SOaH with an absorption maximum at 535 nm.

For comparison purposes a material is cast which on the transparent support only contains the dyed layer (i.e. no colourless underlayer). The silver coating of both layers amounts to 1.5 g/rn.

Both materials are exposed behind a step wedge with red filter and processed as in Example 1. Two colour wedges are obtained parallel to the original whichare measured behind a green filter.

The results of these measurements are given in the following table. The smaller the value of the relative sensitivity log E the higher the sensitivity.

Relative sensitivity log E According to the invention 1.02

According to the prior art 1.29

EXAMPLE 3 According to the prior art 0.81

EXAMPLE 4 The two materials A and B are cast on a transparent support. Material A consists only of a 2.5;; thick layer, containing red-sensitised silver bromide and a cyan image dye. The formula is:

OCH;

and it is used in transmission density of 0.6. The silver content is 0.2 g/m.

Material B comprises two layers, the overlying layer being the same as material A but the underlying layer is of equal thickness, red-sensitised, image dye-free, silver bromide-containing, and has a silver content of 0.2 2

Both materials are exposed behind a stepwedge and red filter and processed as in Example 1. Two colour wedges A and B are obtained parallel to the original which are measured behind red filters. The measurement results can be seen from the appended graph (FIG. 6). The film can be used as a masking film.

EXAMPLE 5 Analogously to Example 4 both materials A and B are cast on a baryta paper with a square metre weight of 160 g. Material A comprises one 2.5;; layer containing red-sensitised silver bromide and a cyan image dye of formula (4) and is used in a reflection density of 1.6. The silver content is 0.22 g/m.

MaterialB comprises two layers, the overlying layer is the same as for material A but the underlying layer is of equal thickness, red-sensitised, image dye-free, silver bromide-containing and with a silver content of 0.2 g/m Processing takes place as in Example 1 and the results are shown in the graph of FIG. 7.

Similar results are obtained if materials A and B are treated in the following dye bleaching baths:

1. Sulphamic acid 80 g. Ascorbic acid 0.3 g. Potassium iodide 30 g. Phenazine l0 mg. Water to 1000 ml.

2. Sulphamic acid 80 g. Ascorbic acid 0.3 g. Potassium iodide 30 g. 2,5-dimethyl-pyrazine 60 mg. Water to [000 ml.

EXAMPLE 6 On a white pigmented cellulose acetate support the following layers are cast in the following sequence:

1. Red-sensitive silver bromide emulsion.

2. Red-sensitive silver bromide emulsion with the cyan dye of Example 4.

3. Intermediate layer.

4. Green-sensitive silver bromide emulsion.

5. Green-sensitive silver bromide emulsion with the purple dye of Example 2.

6. Intermediate layer.

7. Blue-sensitive silver bromide emulsion.

8. Blue-sensitive silver bromide emulsion with the yellow dye of Example 1.

9. Protective layer.

Layers (1) to (8) are 2.0a thick and protective layer (9) 1.3g thick.

The material produced is exposed with white, blue, green and red light and processed as described in Example 1. Measurement of the colour wedges shows that all colours and tonality values are reproduced better than in a material containing no silver bromide auxiliary layers.

We claim:

I. A process for producing a photographic colour image by the silver dye-bleach process, which comprises exposing image wise and processing to a colour image in the presence of a colour bleaching catalyst a photographic material having on a support at least one diffusion-resistant, bleachable azo image dyecontaining silver halide emulsion layer and immediately beneath it on the side away from the light source an image dye-free silver halide emulsion layer, whereby the colour image is produced exclusively by the image dyes present in the photographic material prior to exposure.

2. Process according to claim 1, which comprises exposing and processing a photographic material the halide emulsion layer of which has a sensitivity at least as high as the dye-containing silver halide emulsion layer.

3. Process according to claim 2, which comprises exposing and processing a photographic material the adjacent dye-free and dye-containing silver halide emulsion layers of which are optically sensitised in the same spectral range.

4. Process according to claim 3, which comprises exposing and processing a photographic material the adjacent dye-free and dye-containing silver halide emulsion layers of which are optically sensitised with the same sensitiser.

5. Process according to claim I, which comprises using as the colour bleaching catalyst, a pyrazine, quinoxaline or phenazine.

6. Process according to claim 5, wherein the colour bleaching catalyst is in a photographic processing bath.

7. Process according to claim 5, wherein the dye bleaching catalyst is in one layer of the photographic material to be processed.

8. Process according to claim 1 which comprises exposing and processing a photographic material containing at least two diffusion resistant image dye-containing silver halide emulsion layers, wherein the image dyes differ from one another in their chemical structure and absorption range and wherein the image dye-free silver halide emulsion layers are separated from the underlying image dye-containing silver halide emulsion layers by colourless intermediate layers.

9. Process according to claim 8, which comprises exposing and processing a photographic material the dyefree layer of which is sensitised in the absorption range of the dye of the overlying layer.

10. Process according to claim 8, which comprises exposing and processing a photographic material the dye-free layer of which is sensitised outside the absorption range of the dye of the overlying layer.

11. Process according to claim 9, which comprises using print material as the photographic material.

12. Process according to claim 9, which comprises using a synthetic, organic transparent or pigmented material as the support.

13. Process according to claim 1, which comprises exposing and processing a photographic material the dye-free and dye-containing emulsion layers of which contain the same basic emulsion.

14. A photographic colour image obtained according to the process of claim 1.

15. A photographic colour material which comprises on a support at least one diffusion-resistant, bleachable azo'image dye-containing silver halide emulsion layer and immediately beneath it on the side away from the light source an image dye-free silver halide emulsion layer.

t i t 4 i 

2. Process according to claim 1, which comprises exposing and processing a photographic material the halide emulsion layer of which has a sensitivity at least as high as the dye-containing silver halide emulsion layer.
 3. Process according to claim 2, which comprises exposing and processing a photographic material the adjacent dye-free and dye-containing silver halide emulsion layers of which are optically sensitised in the same spectral range.
 4. Process according to claim 3, which comprises exposing and processing a photographic material the adjacent dye-free and dye-containing silver halide emulsion layers of which are optically sensitised with the same sensitiser.
 5. Process according to claim 1, which comprises using as the colour bleaching catalyst, a pyrazine, quinoxaline or phenazine.
 6. Process according to claim 5, wherein the colour bleaching catalyst is in a photographic processing bath.
 7. Process according to claim 5, wherein the dye bleachinG catalyst is in one layer of the photographic material to be processed.
 8. Process according to claim 1 which comprises exposing and processing a photographic material containing at least two diffusion resistant image dye-containing silver halide emulsion layers, wherein the image dyes differ from one another in their chemical structure and absorption range and wherein the image dye-free silver halide emulsion layers are separated from the underlying image dye-containing silver halide emulsion layers by colourless intermediate layers.
 9. Process according to claim 8, which comprises exposing and processing a photographic material the dye-free layer of which is sensitised in the absorption range of the dye of the overlying layer.
 10. Process according to claim 8, which comprises exposing and processing a photographic material the dye-free layer of which is sensitised outside the absorption range of the dye of the overlying layer.
 11. Process according to claim 9, which comprises using print material as the photographic material.
 12. Process according to claim 9, which comprises using a synthetic, organic transparent or pigmented material as the support.
 13. Process according to claim 1, which comprises exposing and processing a photographic material the dye-free and dye-containing emulsion layers of which contain the same basic emulsion.
 14. A photographic colour image obtained according to the process of claim
 1. 15. A photographic colour material which comprises on a support at least one diffusion-resistant, bleachable azo image dye-containing silver halide emulsion layer and immediately beneath it on the side away from the light source an image dye-free silver halide emulsion layer. 